Beta Decay Process Research Articles

Results from the BRAHMS experiment at RHIC

The coincidence technique can offer a useful way to investigate beta and betabeta decay processes in Ca-48. In this paper the results of a preliminary experimental search are presented. In particular, here the first experimental limit on the half life of the betabeta2nu(0(+)-2(+)) decay of Ca-48 has been obtained; it is T-1/2 > 1.2 x 10(18) y (90% C.L.). (C) 2002 Elsevier Science B.V All rights reserved.

Erratum: “Neutrinoless double beta decay” at a neutrino factory [Phys. Rev. D63, 054031 (2001)

We examine the prospects of detecting an analogous process of neutrinoless double beta decay at a neutrino factory from a high energy muon storage ring. Limits from LEP experiments, neutrinoless double beta decay as well as from global fits have to be incorporated and severely restrict the results. We investigate what limits on light and heavy effective Majorana neutrino masses can be obtained and compare them with existing ones. Discussed are also contributions from right-handed neutrinos and purely right-handed interactions. Other ``new physics'' contributions to the same final state might produce large event numbers.

“Neutrinoless double beta decay” at a neutrino factory

We examine the prospects of detecting an analogous process of neutrinoless double beta decay at a neutrino factory from a high energy muon storage ring. Limits from LEP experiments, neutrinoless double beta decay as well as from global fits have to be incorporated and severely restrict the results. We investigate what limits on light and heavy effective Majorana neutrino masses can be obtained and compare them with existing ones. Discussed are also contributions from right-handed neutrinos and purely right-handed interactions. Other ``new physics'' contributions to the same final state might produce large event numbers.

Is the weak interaction constant really constant?

A comparison is made of the probability of the process of two-neutrino double beta decay for 82Se and 96Zr in direct (counter) and geochemical experiments. The experimental data for 130Te are also analyzed. It is shown that the probability is systematically lower in geochemical experiments, which characterize the probability of ββ (2ν) decay ≍ 109 y ago. It is proposed that this could be due to a change in the weak interaction constant with time. It is proposed that a series of new, precise measurements be performed with the aid of counters and geochemical experiments.

Is the weak interaction constant really constant

A comparison is made of the probability of the process of two-neutrino double beta decay for 82Se and 96Zr in direct (counter) and geochemical experiments. The experimental data for 130Te are also analyzed. It is shown that the probability is systematically lower in geochemical experiments, which characterize the probability of ββ (2ν) decay ≍ 109 y ago. It is proposed that this could be due to a change in the weak interaction constant with time. It is proposed that a series of new, precise measurements be performed with the aid of counters and geochemical experiments.

Investigation of double beta decay of 82Se and 96Zr with tracking detector NEMO-2

To investigate double beta decay processes the NEMO collaboration developed an electron tracking detector made of Geiger cells for track reconstruction and plastic scintillators for energy measurements. The prototype, NEMO-2, is described and results on ββ decay of 82Se and 96Zr are given.

Electromagnetic Form Factors and Static Properties of the Nucleons in a Chiral Symmetric Quark Model

Nucleon charge and magnetic form factors [Formula: see text] are computed in an independent-quark model with an equally mixed scalar and vector confining potential in square root form taking into account the corrections due to center-of-mass motion and pion-clound effects. The values obtained for the nucleon static properties such as the magnetic moment, charge radius and axial vector coupling constant in the neutron beta decay process agree reasonably with the corresponding experimental data. The pseudo-scalar and pseudo-vector pion-nucleon coupling constants are found to be gNNπ=13.43 and fNNπ=0.282, which are in excellent agreement with the experimental data.

Nemo double-beta-decay experiments

To investigate double beta decay processes the NEMO collaboration developed an electron tracking detector made of Geiger cells for track reconstruction and plastic scintillators for energy measurements. The prototype, NEMO-2, is described and results onββ decay of100Mo,116Cd,82Se and96Zr are given. A brief presentation of the status and design parameters of a new detector NEMO-3, which is approximately 20 times larger, will also be given.

Non-collapsing QRPA for neutrinoless double beta decay

The standard quasiparticle random phase approximation(QRPA) is widely used to describe the neutrinoless double beta decay process. Although it has been quite successful in many cases of interest, it has some shortcomings. The most important one is that its solutions collapse for physical values of the particle-particle strength. We shall show that modifications can be done which can extend the validity of this standard QRPA beyond the point of collapse. Such modifications are: The introduction of proton-neutron pairing, the inclusion of the Pauli principle and the extension of the Hilbert space. If all these modifications are introduced into the standard QRPA then the collapse does not occur for physical values of the particle-particle strengths. Thus, one might be able to extract more accurate values on the effective neutrino mass by using the best available experimental limits on the half life of neutrinoless double beta decay.

SHELL MODEL CALCULATIONS FOR HEAVY DEFORMED NUCLEI

The pseudo SU(3) model is shown to be a powerful scheme for describing the excitation spectra as well asB(E2) andB(M1) transition strengths in heavy deformed nuclei. It is also useful for describing double beta decay amplitudes for transitions from the ground state of an even-even nucleus to the ground and excited states of the daughter nucleus, both for the two and zero neutrino emitting modes. The existence of selection rules which strongly restricts the decays is discussed. Anti-correlations between the quadrupole deformation and the Gamow-Teller (GT+) strength are found in an extension of the pseudo SU(3) model which explicitly includes pairing, which is also able to describe the fragmentation of the scissors mode. The projected shell model is introduced and proposed as an alternate means for studying single and double beta decay processes.

Restoration of the Ikeda sum rule in self-consistent quasiparticle random-phase approximation

The so-called self-consistent quasiparticle random phase approximation, accounting for a better treatment of ground-state correlations, is applied to a schematic Hamiltonian, describing the Fermi beta decay process. The self-consistent procedure coupling the BCS minimum with the quantum fluctuations yields an exact fulfillment of the Ikeda sum rule. The role of the ground-state correlations is analyzed in the case of the double beta decay process.

Stimulation of beta decay due to a Bose-Einstein condensate

Nuclear processes can be stimulated by the presence of a macroscopic number of bosons in one of the final states. We describe the conditions necessary to observe the atom-stimulation of a beta decay process. The stimulation may be observable if it becomes possible to produce a Bose-Einstein condensate with the order of 10 14 atoms in a trap.

Double beta decay experiments with the tracking detector NEMO-2

To investigate double beta decay processes the NEMO collaboration developed an electron tracking detector made of Geiger cells and plastic scintillators. The prototype, NEMO-2, is described here and its results on ββ decay of 100Mo and 116Cd are given.

Performance of a prototype tracking detector for double beta decay measurements

To investigate double beta decay processes, the NEMO collaboration began a long-range research and development program in 1988. The NEMO 2 detector, which is now running in the Fréjus underground laboratory (L.S.M. Laboratoire Souterrain de Modane), is the second prototype. It consists of a 1 m 2 source foil sandwiched between Geiger cell drift chambers for electron tracking and two plastic scintillator walls for energy and time-of-flight measurements. The technical description of the detector is followed by the study of the various sources of background.

Study of reactor antineutrino interaction with proton at Bugey nuclear power plant

We report on a high precision measurement at 15m from a 2800 MWth reactor in which 300 000 events of electron antineutrino interactions with proton have been detected using an integral method. The cross section of the neutron inverse beta-decay process has been measured with an accuracy of 1.4%. The ratio of measured cross section to the expected one in the standard V-A theory of weak interactions is: σ ⨍/σ V−A = 98.7% ± 1.4% ± 2.7% = 0.987 ± 0.030 .

The Two-Nucleon Mechanism for the Neutrinoless Double Beta Decay and the BCS Nuclear Wave Function11The project supported by the NSF of China and the Fujian Provincial Science Foundation of China

A method of using the Bardeen–Cooper–Schrieffer (BCS) nuclear wave function to treat the two-nucleon mechanism for neutrinoless double beta decay process is proposed. The neutrinoless decay mode and the neutrinoless decay accompanied by a Majoron emission mode of are studied. Our calculated results show that to reproduce the experimental value of for neutrinoless double beta decai of , the Majorana neutrino mass and the mixing parameter of right-handed current In the emission with a Majoron mode the effective Majoron coupling to neutrino is deduced from the experimental value of for with the result .

Methodology for superallowed Fermi beta-decay Part II. Reduction of data

This paper, Part II of the group, takes the Q EC-values and lifetimes from Part I and reduces them to a form suitable for further analysis in Part III. In reducing the Q EC-values to the phase space factors ƒ critical examination is made of: i) finite nuclear size and form effects; ii) screening by the orbital electrons; iii) finite nuclear mass effects; iv) convolution of the lepton and nucleonic wave functions and v) relativistic terms. In reducing the lifetimes there is a critical discussion of: i) branching ratios; ii) orbital electron capture and iii) the effect of atomic excitation in the beta-decay process.

Estimation of bounds for left-right mixing from nuclear double beta decay processes

Nuclear matrix elements, extracted from a systematic calculation of neutrinoless double beta decay rates for 0 + g.s→o + g.s transitions in 76Ge, 82Se, 128Te, 130Te and 136Xe, have been used to compute bounds on the left-right mixing angle ζ of the weak currents. The parameters of the nuclear model have been fixed by calculating the corresponding two-neutrino double beta decay half lives. The present analysis favours a mixing of the order of |tanξ| < 10 −3 which is to be compared with those obtained in muon decay (|tan ξ| ⩽ 0.035) and in supernova (|tan ξ| ⩽ 10 −5) analysis. It shows that nuclear structure calculations yield estimates on ξ which complement the existing data.

Use of summation methods in the calculation of nuclear double beta decay processes.

The use of summation methods, to deal with the calculation of matrix elements involved in the microscopic description of nuclear double beta decay processes, is discussed. The analysis focuses on the accuracy of a procedure which formally expresses the matrix elements of the standard current-current weak interaction, starting from the second-order perturbation treatment of the standard weak Lagrangian, as divergent power series of energy denominators. It is shown that, when properly treated, the summation method leads to results which coincide with the numerical sum of contributions due to virtual intermediate states.

Beta rays and neutrinos

It was over 30 years between the first observation of the enigmatic process of beta decay and the first postulation of the neutrino. It took a further 26 years until the first neutrino was detected and yet another 27 until the electroweak theory was confirmed by the discovery of W and Z particles. This article traces some of the puzzles and paradoxes associated with the history of the neutrino.